//! 数据复制管理模块
//! 
//! 负责集群中数据的复制、同步和一致性保证。

use crate::{Error, Result};
use super::{ClusterConfig, ClusterEvent};
use std::collections::HashMap;
use std::time::SystemTime;
use serde::{Serialize, Deserialize};
use tokio::sync::mpsc;

/// 复制管理器
#[derive(Debug)]
pub struct ReplicationManager {
    /// 集群配置
    config: ClusterConfig,
    /// 复制状态
    replication_state: ReplicationState,
    /// 复制日志
    replication_log: Vec<ReplicationEntry>,
    /// 节点复制状态
    node_states: HashMap<String, NodeReplicationState>,
    /// 事件发送器
    event_sender: Option<mpsc::UnboundedSender<ClusterEvent>>,
}

/// 复制状态
#[derive(Debug, Clone)]
pub struct ReplicationState {
    /// 当前复制因子
    pub current_replication_factor: usize,
    /// 目标复制因子
    pub target_replication_factor: usize,
    /// 复制延迟（毫秒）
    pub replication_lag_ms: u64,
    /// 同步状态
    pub sync_status: SyncStatus,
}

/// 同步状态
#[derive(Debug, Clone, PartialEq)]
pub enum SyncStatus {
    /// 同步中
    Syncing,
    /// 已同步
    Synced,
    /// 延迟
    Lagging,
    /// 失败
    Failed,
}

/// 复制条目
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ReplicationEntry {
    /// 条目ID
    pub entry_id: u64,
    /// 数据操作
    pub operation: DataOperation,
    /// 时间戳
    pub timestamp: SystemTime,
    /// 源节点
    pub source_node: String,
    /// 目标节点
    pub target_nodes: Vec<String>,
    /// 复制状态
    pub status: ReplicationEntryStatus,
}

/// 数据操作
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DataOperation {
    /// 插入
    Insert {
        table: String,
        key: String,
        value: Vec<u8>,
    },
    /// 更新
    Update {
        table: String,
        key: String,
        value: Vec<u8>,
    },
    /// 删除
    Delete {
        table: String,
        key: String,
    },
    /// 批量操作
    Batch {
        operations: Vec<DataOperation>,
    },
}

/// 复制条目状态
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum ReplicationEntryStatus {
    /// 待复制
    Pending,
    /// 复制中
    Replicating,
    /// 已完成
    Completed,
    /// 失败
    Failed,
}

/// 节点复制状态
#[derive(Debug, Clone)]
pub struct NodeReplicationState {
    /// 节点ID
    pub node_id: String,
    /// 最后同步时间
    pub last_sync_time: SystemTime,
    /// 复制延迟
    pub replication_lag: u64,
    /// 待复制条目数
    pub pending_entries: usize,
    /// 复制吞吐量（条目/秒）
    pub replication_throughput: f64,
}

impl ReplicationManager {
    /// 创建新的复制管理器
    pub fn new(config: ClusterConfig) -> Result<Self> {
        Ok(Self {
            replication_state: ReplicationState {
                current_replication_factor: 1,
                target_replication_factor: config.replication_factor,
                replication_lag_ms: 0,
                sync_status: SyncStatus::Synced,
            },
            config,
            replication_log: Vec::new(),
            node_states: HashMap::new(),
            event_sender: None,
        })
    }
    
    /// 启动复制管理器
    pub async fn start(&mut self) -> Result<()> {
        tracing::info!("启动复制管理器");
        
        // 初始化节点状态
        self.initialize_node_states().await?;
        
        // 启动复制监控
        self.start_replication_monitor().await?;
        
        tracing::info!("复制管理器启动完成");
        Ok(())
    }
    
    /// 停止复制管理器
    pub async fn stop(&mut self) -> Result<()> {
        tracing::info!("停止复制管理器");
        Ok(())
    }
    
    /// 初始化节点状态
    async fn initialize_node_states(&mut self) -> Result<()> {
        // 简化实现：为当前节点创建状态
        let node_state = NodeReplicationState {
            node_id: self.config.node_id.clone(),
            last_sync_time: SystemTime::now(),
            replication_lag: 0,
            pending_entries: 0,
            replication_throughput: 0.0,
        };
        
        self.node_states.insert(self.config.node_id.clone(), node_state);
        
        Ok(())
    }
    
    /// 启动复制监控
    async fn start_replication_monitor(&self) -> Result<()> {
        tracing::debug!("启动复制监控");
        
        // 简化实现：实际需要启动后台任务监控复制状态
        
        Ok(())
    }
    
    /// 复制数据操作
    pub async fn replicate_operation(&mut self, operation: DataOperation) -> Result<u64> {
        let entry_id = self.replication_log.len() as u64 + 1;
        
        let entry = ReplicationEntry {
            entry_id,
            operation,
            timestamp: SystemTime::now(),
            source_node: self.config.node_id.clone(),
            target_nodes: self.get_target_nodes(),
            status: ReplicationEntryStatus::Pending,
        };
        
        tracing::debug!("添加复制条目: {}", entry_id);
        self.replication_log.push(entry);
        
        // 开始复制
        self.start_replication(entry_id).await?;
        
        Ok(entry_id)
    }
    
    /// 获取目标节点
    fn get_target_nodes(&self) -> Vec<String> {
        // 简化实现：返回空列表
        // 实际需要根据复制策略选择目标节点
        Vec::new()
    }
    
    /// 开始复制
    async fn start_replication(&mut self, entry_id: u64) -> Result<()> {
        if let Some(entry) = self.replication_log.iter_mut().find(|e| e.entry_id == entry_id) {
            entry.status = ReplicationEntryStatus::Replicating;
            
            tracing::debug!("开始复制条目: {}", entry_id);
            
            // 简化实现：直接标记为完成
            // 实际需要向目标节点发送复制请求
            entry.status = ReplicationEntryStatus::Completed;
        }
        
        Ok(())
    }
    
    /// 处理复制请求
    pub async fn handle_replication_request(&mut self, entry: ReplicationEntry) -> Result<()> {
        tracing::debug!("处理复制请求: {}", entry.entry_id);
        
        // 应用数据操作
        self.apply_operation(&entry.operation).await?;
        
        // 更新节点状态
        if let Some(node_state) = self.node_states.get_mut(&entry.source_node) {
            node_state.last_sync_time = SystemTime::now();
        }
        
        Ok(())
    }
    
    /// 应用数据操作
    fn apply_operation<'a>(&'a self, operation: &'a DataOperation) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<()>> + Send + 'a>> {
        Box::pin(async move {
            match operation {
                DataOperation::Insert { table, key, value: _ } => {
                    tracing::debug!("应用插入操作: {} -> {}", table, key);
                    // 简化实现：实际需要调用存储引擎
                }
                DataOperation::Update { table, key, value: _ } => {
                    tracing::debug!("应用更新操作: {} -> {}", table, key);
                    // 简化实现：实际需要调用存储引擎
                }
                DataOperation::Delete { table, key } => {
                    tracing::debug!("应用删除操作: {} -> {}", table, key);
                    // 简化实现：实际需要调用存储引擎
                }
                DataOperation::Batch { operations } => {
                    tracing::debug!("应用批量操作: {} 个操作", operations.len());
                    for op in operations {
                        self.apply_operation(op).await?;
                    }
                }
            }

            Ok(())
        })
    }
    
    /// 处理故障转移
    pub async fn handle_failover(&mut self, failed_node: &str) -> Result<()> {
        tracing::info!("处理节点故障转移: {}", failed_node);
        
        // 移除失败节点的状态
        self.node_states.remove(failed_node);
        
        // 重新分配复制任务
        self.reassign_replication_tasks(failed_node).await?;
        
        // 发送分片重新平衡事件
        if let Some(sender) = &self.event_sender {
            let _ = sender.send(ClusterEvent::ShardRebalanced);
        }
        
        Ok(())
    }
    
    /// 重新分配复制任务
    async fn reassign_replication_tasks(&mut self, failed_node: &str) -> Result<()> {
        tracing::debug!("重新分配复制任务，失败节点: {}", failed_node);
        
        // 查找包含失败节点的复制条目
        for entry in &mut self.replication_log {
            if entry.target_nodes.contains(&failed_node.to_string()) {
                // 移除失败节点
                entry.target_nodes.retain(|node| node != failed_node);
                
                // 添加新的目标节点
                // 简化实现：实际需要根据复制策略选择新节点
                
                // 重新开始复制
                if entry.status != ReplicationEntryStatus::Completed {
                    entry.status = ReplicationEntryStatus::Pending;
                }
            }
        }
        
        Ok(())
    }
    
    /// 获取复制状态
    pub fn get_replication_state(&self) -> &ReplicationState {
        &self.replication_state
    }
    
    /// 获取节点复制状态
    pub fn get_node_state(&self, node_id: &str) -> Option<&NodeReplicationState> {
        self.node_states.get(node_id)
    }
    
    /// 获取所有节点状态
    pub fn get_all_node_states(&self) -> Vec<&NodeReplicationState> {
        self.node_states.values().collect()
    }
    
    /// 检查复制健康状态
    pub async fn check_replication_health(&mut self) -> Result<()> {
        let now = SystemTime::now();
        
        // 检查复制延迟
        let mut max_lag = 0u64;
        for (node_id, state) in &mut self.node_states {
            if let Ok(elapsed) = now.duration_since(state.last_sync_time) {
                let lag_ms = elapsed.as_millis() as u64;
                state.replication_lag = lag_ms;
                max_lag = max_lag.max(lag_ms);
            }
        }
        
        // 更新复制状态
        self.replication_state.replication_lag_ms = max_lag;
        
        // 更新同步状态
        self.replication_state.sync_status = if max_lag < 1000 {
            SyncStatus::Synced
        } else if max_lag < 5000 {
            SyncStatus::Lagging
        } else {
            SyncStatus::Failed
        };
        
        Ok(())
    }
    
    /// 设置事件发送器
    pub fn set_event_sender(&mut self, sender: mpsc::UnboundedSender<ClusterEvent>) {
        self.event_sender = Some(sender);
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[tokio::test]
    async fn test_replication_manager_creation() {
        let config = ClusterConfig::default();
        let replication_manager = ReplicationManager::new(config).unwrap();
        
        assert_eq!(replication_manager.replication_state.current_replication_factor, 1);
        assert_eq!(replication_manager.replication_state.target_replication_factor, 3);
        assert_eq!(replication_manager.replication_state.sync_status, SyncStatus::Synced);
    }
    
    #[tokio::test]
    async fn test_data_operation_replication() {
        let config = ClusterConfig::default();
        let mut replication_manager = ReplicationManager::new(config).unwrap();
        
        let operation = DataOperation::Insert {
            table: "users".to_string(),
            key: "user1".to_string(),
            value: b"user_data".to_vec(),
        };
        
        let entry_id = replication_manager.replicate_operation(operation).await.unwrap();
        
        assert_eq!(entry_id, 1);
        assert_eq!(replication_manager.replication_log.len(), 1);
        
        let entry = &replication_manager.replication_log[0];
        assert_eq!(entry.entry_id, 1);
        assert_eq!(entry.status, ReplicationEntryStatus::Completed);
    }
    
    #[tokio::test]
    async fn test_failover_handling() {
        let config = ClusterConfig::default();
        let mut replication_manager = ReplicationManager::new(config).unwrap();
        
        // 添加一个节点状态
        let node_state = NodeReplicationState {
            node_id: "failed-node".to_string(),
            last_sync_time: SystemTime::now(),
            replication_lag: 0,
            pending_entries: 0,
            replication_throughput: 0.0,
        };
        replication_manager.node_states.insert("failed-node".to_string(), node_state);
        
        // 处理故障转移
        replication_manager.handle_failover("failed-node").await.unwrap();
        
        // 验证节点状态已被移除
        assert!(!replication_manager.node_states.contains_key("failed-node"));
    }
    
    #[tokio::test]
    async fn test_replication_health_check() {
        let config = ClusterConfig::default();
        let mut replication_manager = ReplicationManager::new(config).unwrap();
        
        // 初始状态应该是同步的
        replication_manager.check_replication_health().await.unwrap();
        assert_eq!(replication_manager.replication_state.sync_status, SyncStatus::Synced);
    }
}
